East Texas HVAC, done the Taylor way

From a load calculation on the house — insulation, windows, orientation and ductwork — not from the old unit. An oversized system cools the air before it can remove the humidity and wears itself out cycling.

The indoor coil and outdoor unit are matched to each other for capacity and refrigerant. Replacing one and not the other usually costs efficiency and can void the manufacturer's rating.

Low airflow from a clogged filter or coil, low refrigerant from a leak, a failed capacitor or a frozen coil are the common causes, and each looks the same from the thermostat.

Ice on the line or coil means the coil is running too cold — usually restricted airflow or low refrigerant. Turning the system off to thaw it is the first step; finding the cause is the second.

Rooms the central system does not reach, additions, garages, sunrooms and houses with no ductwork. Each head conditions its own zone, so each room can hold a different temperature.

Where it can throw air across the room rather than into a wall or a doorway, high on a wall with clearance around it, and where the line set can reach the outdoor unit without a long exposed run.